What would you say is a fair payment threshold?
May be I am wrong but I personally prefer 0 payment threshold with fee of 1% (sumo.fairpool.xyz) or 0.1 min payout and 0.5% fee (sumopool.sonofatech.com). 0% fee is interesting for high power miners not amateur ones like me.
It's not particularly hard yet to achieve 1SUMO at the moment. If you planned on keeping SUMO for long time, 0% fee would be definitely benefit you better.
In my case, I am too lazy to change to new pool at the moment :\